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Topic: Recent experiments (Read 28447 times)

In my first GH cclock, I used brass bushings and steel pivots. They require oil every two or three years but have done very well and are nearly 20 years old and show little wear. Lately I have been using miniature ball bearings and they work very nicely with little friction. I am concerned about dust and possibly bugs getting into them since they are not shielded. I can't be sure yet how they will stand the test of time. They don't need oil, however. and that is a plus. I could use shielded bearings but they have more friction.

Recently I turned a 1/16 pivot on the end of an ebony arbor and fitted it into a lignum vitae bushing. It seems to work very smoothly and with little friction. The lignum vitae produces its own natural oil lubrication so it should wear well but it needs time to see how it holds up. The very small diameter of the wooden pivot gave me some concern until I tried it, but it seems surprisingly strong and I think it will work sell on all but the great wheel arbors. Moreover, I think I could expand its size to 3/32 or even 1/8 without adding greatly to the friction.

It is easy to fit these wooden parts too. Once the pivot is turned, a slightly smaller hole is drilled in the bushing and then reamed with standard clock reamers to get a good fit. I recently bought a set of these reamers or "broaches" on Ebay for about $12. I plan to use this method in my next clock. It will eliminate all metal parts and save the cost of the ball bearings.

Teflon would pobably work well too but I resist the use plastic for aesthetic reasons and because I like to be able to say I have made an all wood clock.

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JoeComunale

The use of Lignum Vitae as a bushing material for clock pivots goes back quite a few years. In fact, John Harrison, the inventor of the Grasshopper Escapement (also the brass/steel grid iron pendulum - a temperature compensating pendulum rod, and rumored to be the inventor of the ball bearing) - used Lignum Vitae bushings in his Brocklesby Park Tower Clock (then a clock over a stable) with Brass Pivots. (From "The Illustrated Longitude" by Dava Sobel and William Andrewes)

The Brocklesby Park Clock is still operating (with some maintenance) - almost 300 years later - in the near vicinity of the sea (lots of humidity, salt, cold/hot weather, etc.). Quite an accomplishment.

So - it sounds like good advice to experiment with this.

I don't have any lignum vitae - but I do have Ipe', that I am experimenting with making clock pivot bushings.

Process:I first cut the .5" bushings from the face of an Ipe' board using my Veritas "Snugplug" tapered cutters.

Then I drill a .5" hole about .375-.5 deep, in an oak dowel mounted in the 3-jaw chuck of my metal lathe. Next I drill a 0.25" hole the whole way through the oak plug - for an ejection rod to enter.

I insert the tapered bushing in the oak dowel- and center drill, then drill an undersized hole for the clock pivot.

The final hole is reamed out slightly oversized (about .002" I think). This seems to make a nice pivot for my initial trials.

To remove I have an ejection rod that I insert into the outboard side of the headstock - and pop the ipe bushing plug out of the oak dowel.

(If you have a better idea - or questions - please post)

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JayRay_Hughes

After jrbeall’s suggestion, and Joes post, I am going to consider lignum. 300 years. Holly cow. I to fancy the idea of an all wood clock, but also find myself wanting to build the best. I am not a details person so much but when I really get into something then I tend to want perfection. With perfection, come the details.

Reaming is a new idea to me. I definitely see the benefit. I am glad you mentioned this.

Is Ipe as oily as lignum? What other woods would be as good or possible better?

When using lignum, would I use lignum on lignum or just on the bushing?

JoeComunale

Ipe' is also known as Brazilian Walnut, and goes by quite a few other names ( too late in the evening to remember them all). I am not sure if Ipe is as oily as Lignum Vitae or not. My guess is that it is very similar but possibly with less advantages. (Why? Because men like John Harrison had a very intimate knowledge of woods, their growth, etc - and he happened to pick lignum vitae. I think it was no accident. Also, Ipe' is grown in the same areas as Lignum Vitae - so they were both probably available at the same time. That's why.)

Lignum Vitae is slightly harder than Ipe - with a 4500 Janka hardness rating as compared to 3650 for Ipe' - which means that they are both about 3-4 times harder than Ash or Rock Maple!

Ipe' is very oily and resists rot and fire damage similarly to Lignum Vitae.

I just used it because I have it. I expect very similar results as lignum vitae. But - I will say - if I had both - I would use Lignum Vitae over Ipe'.

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Marc

Lignum vitae will secreate the resin over the axle and eventually seize it in the early running of the timepiece. This happened to me and others who used it as a bearing. I had to clean off the axle and bearing with a Q-tip dipped in Naptha two or three times the first year it ran. Have not had any problems in the last few years.

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JoeComunale

The Ipe' that I am using isn't that oily. When I look at the drilled and reamed surfaces - I see very "shiny" smooth surfaces. I don't see oil. However, as I am drilling it with a plug cutter - it does smoke a lot - even at slow speeds. So - I will have to keep you posted on how the first clock works with this as a bushing material.

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Harry

Hi Have just joined in on your site and have been reading most of the posts with interest . Thought you may like to know where you can get Lignum Vitge fairly cheap , I read many years ago that lawn bowls where made from it , Over the years I checked out a few garage sales etc most modern ones seem to be made of some form of plastic but eventually found myself two balls with enough wood to last many clocks , for the princley sum of two dollars .. I am not to sure if lawn bowls is as popular in the US as it is in Australia but I am sure you could find some ..

JoeComunale

I am just in the process of watching the George Bruno Video Tapes (Borrowed from the NAWCC library), and he does several things to a bushing:

1) Cuts them with a knife to get a smooth edge (although - he's not using lignum vitae)

2) after seating and removing a lot of the material from the back side (outside) of the plates (this is critical to reduce the bearing area of the bushing) - he burnishes with a clock bushing burnisher.

George stated that he made his out of coat hanger held against a belt/disk sander to get the taper (no doubt mounted in a hand drill would help this along a good bit). Then he burnishes/reams on the drill press - running at fairly high speeds.

This will result in a tapered bearing area for the pivot - and should reduce the friction in the gear train.

If you get a chance - Join NAWCC, they have a marvelous library - and tape loan program.

Rockler woodworking (http://www.rockler.com) in the US has "Argentine Lignum Vitae" turning blanks. It is similar, although not identical to true Lignum Vitae. The botanical name is Bulnesia Sarmientoi.

I noticed Joe's mention of burnishing! I have been giving this some serious thought. Fact is, I turned a 2" piece of 1/4" steel stock down to 1/8" for about 3/8" and mounted it in my table mounted router. Also tried dogwood made the same. Too much presher caused the dogood to brake, the steel does OK. Polished or burnished all gears and pinions, the results seem to justify the added time. Now with the complete running train assemblied without the virge, I can gently blow on the escape wheel and all turn extremly smothe. Has any one tried waxing and polishing the contact area of the escape wheel and or the virge?? If so, what kind of wax?Bruce